Elastic fluid turbine turning gear control system



H. BANY June 10, 1941.

ELASTIC FLUID TURBINE TURNING GEAR CONTROL SYSTEM Filed Oct. 19, 1939 2 Sheets-Sheet l lhventor: Herman Bang, 'fi awmwfl June 10, 1941. H, BANY 2,245,175

ELASTIC FLUID TURBINE TURNING GEAR CONTROL SYSTEM Filed .Oct. 19, 1939 2 Sheets-Sheet 2 Fig. 6.

Inventor: Herman Barns i-i IS Attorney.

Patented June 10, 1941 ELASTIC FLUID TURBINE TURNING GEAR CONTROL SYSTEM Herman Bany, Lansdowne, Pa., assig'nor to General Electric Company, a corporation of New York Application October 19, 1939, Serial No. 300,197

10 Claims.

The present invention relates to control systems, particularly for apparatus for slowly rotating the rotor of an elastic fluid turbine during shutdown periods.

In steam turbine practice it has been found desirable to turn the rotor of the turbine, particularly after having been shut down, at a speed of the order of one or two R. P. M. The turbine rotor may thereby be cooled uniformly, and creeping or sagging of the shaft will be precluded as well as the formation of internal stresses. This slow speed turning is usually accomplished by means of an electric motor and speed reducing gearing connected to the turbine shaft. An auxiliary lubricating oil pump is also provided for supplying lubricating oil to the bearings of the turbine when it is being driven by the turning gear motor. When steam is admitted to the turbine preparatory to the bringing of the machine up to normal operating speed, the turning gear is disconnected from the turbine shaft and the auxiliary oil pump stopped.

It is an object of this invention to provide a new and improved electrical control system for an elastic fluid turbine turning gear apparatus.

Another object of my invention is to provide a new and improved electrical control system for an elastic fluid turbine turning gear apparatus including an auxiliary lubricating system which is adapted for manual control during shutdown periods of the turbine and for automatic control by the turbine when it is being started up or being shut down.

For a consideration of what I believe to be novel and my invention, attention is directed to the following description and the claims appended thereto taken in connection with the accompanying drawings. In the drawings, Fig. l illustrates a diagrammatic view of a turbine equipped with a turning gear mechanism and an auxiliary oil lubricating system; Fig. 2 is a sectional view of the turning gear mechanism illustrating certain features thereof; and Fig. 3 is a wiring diagram illustrating the control system for the turning gear and the auxiliary lubricating apparatus of the arrangement shown in Fig. 1.

The power plant arrangement as shown in Fig. 1 comprises an elastic fluid turbine it] provided with an inlet steam chest it and an exhaust hood 92. During periods of shutdown the turbine rotor is adapted to be turned at a relatively slow speed by means of a turning gear mechanism which in the present instance comprises an electric motor i3 connected to the turbine shaft it through suitable speed reducing gearing indicated at E5. The lubricating system for the main turbine bearings 86 and ii comprises a lubricant storage reservoir 18 in which is usually arranged the main oil pump it. During the normal operation of the turbine the lubricating oil pump l9 will draw oil through the non-retum inlet port 2| and discharge it through connection 22, the check valve 23, feeder lines 24 and 25, to the turbine bearings 16 and I1, respectively. Oil is drained from the turbine bearings by conduits 26 and 21 and returned to the reservoir l8.

An auxiliary oil pump 29 is provided for circulating the lubricating oil through the turbine bearings when the turbine is rotated by the tuming gear motor. The pump 29 is adapted to withdraw oil from the storage reservoir I 8 through the check valve 30 bypassing the main pump IS, the connection 22, and discharge it through the connection 32, the check valve 33, into the feeder lines 24 and 25. A suitable oil pressure responsive device 34 is provided in the pump outlet connection 32, having contact 35 which is adapted to be moved to the closed circuit position upon the occurrence of a predetermined suitable oil pressure. To indicate that oil is properly circulating through the bearings of the turbine, a flow responsive device 36 is arranged in the drain connection from the bearings to the reservoir, which device is provided with contact 31 that is adapted to be moved to the closed circuit position upon the occurrence of proper oil flow through the drain conduit. The auxiliary oil pump 29 is adapted to be driven by either of a pair of motors 38, 39 which may be connected to different sources of power and are controlled, as will be later described, so that in the event of power failure of one source, the other motor will be immediately connected in service to insure a continuity of lubricant circulation.

Suitably connected for actuation by the turbine shaft i4 is a speed responsive device 4| provided with a circuit making and breaking switch indicated at 63 which is normally closed and adapted to be moved to the open circuit position upon the turbine shaft being rotated at a speed greater than approximately one R. P. M. Although any suitable speed responsive device may be used, I prefer to use a device such as that described in the Patent No. 2,129,534, Newell, issued Septembar 6, 1938, and assigned to the assignee of the present invention. A device or the type described in'this patent is accurately responsive to extremely slow rotational speeds, as of the order of one R. P. M.

Referring to Fig. 2, the turning gear motor i3 is suitably connected to the speed reducing gearing as by a belt 50. The speed reducing gearing may comprise a suitably arranged train of gears, such as 58, 52, 53 and 54. Torque is transmitted from the gear 54 to the turbine rotor through the gear 55 which is adapted for shiftable movement into and out of engagement with the gear 56 secured to and forming a part of the turbine rotor. The gear 55 normally has the lowest speed of the speed reducing gearing and is accordingly subjected to a high specific tooth premre. It is therefore important with respect to this gear that the torque be uniformly transmitted through the entire length of its teeth. For this reason the gear is yieldingly supported so that it may adjust itself during operation by means including the yoke 51' which is suitably slotted at 58, for receiving the ends of the gear shaft and is secured to the lower half 59 of the gear casing. The gear 55 may be moved into and out of engagement with the gear 56 by means including a lever 60 which is fulcrumed on the shaft of gear 54. Connected to the lever 60 is an extension BI which is connected by link 62 to the armature 83 of the electromagnetic operating device 64. The gear 55 is normally biased to the non-engaging position by means of the spring 65 attached to the operating lever 6|. Upon the energization of the electro-magnetic device 84, the end of the operating lever 6| is raised upwardly to rotate the gear 55 about the axis of gear 54 to bring the former into meshing engagement with the turbine rotor gear 56. A suitable switch 65 is operatively associated with the mechanism to indicate the position of the gear 55. The switch 66 is provided with a downwardly biased stem 61 which, for example, may be engaged by the operating lever 6| as it is moved upwardly to the gear engaging position. Arranged for actuation by the stem .61 are contacts 68, 69 and I which are adapted to be moved to the open circuit position as lever BI is moved upwardly, and contact II which is adapted to be closed simultaneously with the opening of the other contacts.

The operation of the turbine turning and lubricating apparatus is adapted for control by a manual pushbutton start switch which, when depressed, automatically starts the lubricating oil pump and after suitable oil pressure is built up and suitable oil flow through the turbine bearings takes place, the turning motor I3 will be energized. After the turning motor has started, the gear 55 is shifted into engagement with the turbine rotor gear 56. The operation of the turbine turning apparatus. and lubricating oil system will continue until a manual pushbutton stop switch is depressed or until steam is admitted to the turbine and the latter is thereby rotated at a speed greater than one R. P. M., when the turbine turning motor will automatically be disconnected from the turbine shaft and the auxiliary lubricating oil pump driving motor will be automatically deenergized. In the shutting down of the power plant, when the turbine speed has dropped to approximately one B. P. M., the auxiliary oil pump is again started up and the tuming gear motor is again energized and automatically coupled to the turbine rotor.

Referring now to the schematic wiring diagram of Fig. 3, the control system will be more completely described. Power -is adapted to be supplied to the apparatus of the control system from a suitable direct current source, such as 125 volts, indicated by the positive and negative supply leads I5 and I8, respectively. Certain pieces of apparatus of the system require, or are more appropriately energized from, a source of alternating current which may be supplied through leads I1 and 18. A manual starting control switch I9, normally biased to the open circuit position by means of a suitably arranged spring 8I, is provided which, when closed, completes an energizing circuit for the winding 83 of the relay 84. As the relay 84 picks up, it is latched in by the catch 85 while the series contacts 99 thereof are moved to the open circuit position by stop 81 to deenergize the winding 83. Contacts 88 of the relay 84 close to condition the circuit of the latch tripping solenoid 89 for energization at a later time. The circuit for the latch tripping solenoid 89 includes the normally open contact of the manual pushbutton stop switch 90 and normally open contact II of the position indicating switch 66 associated with the turbine turning mechanism. The switch 90 is biased to the open position by means of a suitably arranged spring 82. It will here be noted that the contact II is closed only when the turning gear is engaged, which safeguards against tripping of the relay 94 at any other time and insures that the turbine will automatically go on turning gear upon shutdown from operation by steam. A circuit is also completed for the energizing element 9I of the speed responsive device M, which circuit extends from the alternating current supply line 'I'I through the closed contacts 92 of relay 84, through the energizing element 9| of the speed responsive device M, the normally closed contacts 68 of the position switch 68, to the other alternating current supply line I8. Since the turbine is at standstill, the switch 43 of the speed responsive device 4| will be actuated to the contact-making position so as to connect the winding 94 of the auxiliary relay 95 across the direct current supply lines 15 and 15. As the relay 84 picks up, circuits are established for energizing both auxiliary pump motors 38 and 39. The control circuit for these motors extends from the supply line 15 through the closed contact 95 of the deenergized relay 91, the closed contact 90 of the control relay 84, line 99, closed contact ml of relay 95, the winding of relay I02, to the other supply line 18. As relay I02 picks up, its contact I03 completes a holding circuit around the contacts WI, and its contact I04 completes an energizing circuit for the alternating current contactor I05 which, in turn, picks up its contact I06 to connect the motor 38 across the alternating current supply lines TI and I8. If for any reason the alternating current source of supply fails during either the starting or shutting down periods, the second motor 39 will be energized to maintain the operation of the oil pump 29. The contactor I 05 is provided with a second contact I 01 which in the deenergized condition of contactor I05, completes an energizing circuit for the relay I08. The circuit for the latter relay extends from the energized line 99 through closed contactor I05 is provided with a second contact I01 of the contactor I05, through the winding of the relay I08, to the other supply line 16. As the relay I08 picks up, its contact 2 completes a holding circuit around the contacts IOI of relay 95 while its contact II3 completes an energizing circuit for the auxiliary contactor I I4 which picks up its contact II5, thereby connecting the auxiliary direct current motor 39 across a suitable direct current source of supply, such as 550 volts, represented by lines H6 and Ill. Upon the reestablishment of the alternating current source of supply, the contactor I05 will pick up to efiect the energization of the alternating current motor 38 and deenergization of motor 39.

Upon the closure of contact 98 of the control relay 84, another circuit is completed for effecting the energization of the time delay dropout relay II8. This latter circuit extends from the energized line 99, through line H9, the closed contact I2I of the deenergized relay I22, through the winding of the relay H8, to the other direct current supply line I6. The relay I I8 picks up to close its contact I23 and upon proper operation of the lubricating oil system, as indicated by the closure of the cont-acts 35 of the oil pressure responsive device 34 and closure of contacts 31 of the oil flow responsive device36, the control relay I24 will be energized to effect the energization of the turbine turning gear motor I3. The circuit for the control relay I24 may be traced from the energized line II9, through the closed contacts 35 and 31 of the oil pressure and oil flow responsive devices 34 and 36, respectively, the closed contact I25 of the auxiliary relay 95, the closed contact I23 of the relay II8, through the winding of the control relay I24, to the other supply line I6. As the relay I24 picks up, its contact I26 completes a holding circuit for itself around the contacts I25 and I23 of the relays 95 and H8, respectaively. A second contact I2'I of the relay I24 completes an energizing circuit for the contactor I28 which picks up its contact I29 to connect the turbine turning gear motor I3 directly across the alternating current supply lines 11 and I8.

The closed contact I3I of the contactor I28 completes an energizing circuit for the relay I22. This relay when energized opens its contact I2I to deenergize the relay II8 but because of the time delay device I32 associated with the latter relay, its dropout will be delayed for a few seconds in order to give the motor I3 time to come up to normal speed. A second contact I33 of the relay I22 will be moved to the closed circuit po-' sition and after relay II8 drops out, the contact I34 of the latter will close to complete an energizing circuit for the time delay dropout relay I35, which circuit extends from the energized conductor II9 through the closed contact I33 of relay I22, the closed contact I36 of the relay 95, the closed contact I34 of the relay II8, the closed contact I0 of the position switch 66, through the winding of relay I35, to the other supply line IS. The relay I35 will pick up its contact I31, thereby completing an energizing circuit for the winding of the solenoid 64 which will effect the coupling of the turbine turning gear to the turbine rotor shaft by shifting the gear 55 into engagement with the turbine shaft gear 56. After this coupling has been eflected, the position switch 66 will be shifted upwardly by the engagement of the lever 6| with the switch stem 61, thereby opening contact I8 and deenergizing the relay I35 which in turn will drop out with a suitable time delay, as determined by the setting of the mechanism I38, to deenergize the solenoid 64. It is to be understood that continuous energization of the solenoid operating device 64 is not required for maintaining the coupling between the turbine turning motor I3 and the turbine rotor. It will be noted from an inspection of the gearing arrangement of Fig. 2 that when the gear 55, being driven in the direction indicated, is brought into mesh with the turbine rotor gear 56, the gear 55 will be maintained in the engaging position by the forces acting during the transmission of torque from the motor to the g turbine.

If it is desired to start up the turbine, steam is admitted thereto while the turning gear motor is slowly rotating the'turbine rotor.

At a turbine speed greater than one R. P. M. the contacts 43 of the speed responsive device 4| are open-circuited and relay 95 will drop out. The turbine turning gear motor I3 and the auxiliary oil pump motor will be deenergized upon the opening of contact 96 of relay 91. With regard to this latter relay, it will be noted that when the turning gear was first shifted to the engaged position and the position of switch 66 was moved upwardly, the contact 69 thereof was moved to the open circuit position deenergizing the relay I which thereupon closed its contact arm I42. When the turning gear is shifted to the disengaged position upon the acceleration of the turbine, the contact 69 is reclosed to again energize the relay I4I. Due to the time delay restrain device I43 of the latter relay, the circuit will be closed for temporarily energizing relay 91 in parallel with relay I4I. As the contact 96 of relay 91 opens, line 99 will be deenergized and hence also the pump motor control relay I02 and relay I98 if it had been energized. Relay I24 will also be deenergized which in turn will cause contactor I28 to drop out and shut down the turning gear motor I3. After a short time delay, relay I4I will pick up its arm I42 and deenergize the relay 9'! which will close its arm 96 to recondition the system for a subsequent starting.

When it is decided to shut down the power plant and the supply of steam to the turbine is cut off, the turbine rotor will automatically be recoupled with the turning gear for rotation thereby during the cooling period of the turbine. As the turbine speed drops to a value of about 1 R. P. M. the switch 43 of the speed responsive device M will move to the closed circuit position effecting the energization of the control relay 95. As the relay 95 is moved to the closed circuit position, the appropriate oil pump motor and the turning gear motor will be started automatically and the turning gear connected to the turbine rotor in a manner as described above. The turbine will be rotated continuously under proper lubrication at a speed of about 1 R. P. M. until it is again started up by steam or until it is brought to a standstill after the turbine rotor has thoroughly cooled.

The turning gear apparatus may be deenergized and the turbine brought to a standstill by depressing the manually operable stop switch 98 thereby completing an energizing circuit for the trip coil 89 which will actuate the latch 85 to the releasing position to allow the relay 84 to drop out. As the contact arm 98 of the latter relay opens, the auxiliary oil pump driving rotor and the turning gear motor will both be deenergized.

When the turning gear apparatus is thus deenergized the turning gear will normally remain coupled with the turbine rotor and as a result the switch 66 will be maintained in its upper position during the standstill condition of the turbine. An auxiliary contact arm I44 is provided on the stem of the relay I22 which contact arm in the deenergized condition of the relay completes a circuit bridging the contact 68 of the position switch 66. Should it be desired to place the turbine on turning gear operation again, the

, starting control push button 19 will be depressed energizing the relay 84 and the circuit for the energizing element 9| of the speed responsive device 4| will be completed through contacts 92 of the relay 84 and contact I44 of the deenergized relay I 22. The remaining circuits for the starting sequence will be energized in the proper order substantially as described above.

turning gear apparatus including a motor and a turbine bearing lubricating system including anauxiliary oil pump motor, a control switch, means for initiating the operation of said pump motor upon the actuation of said switch, means responsive to predetermined conditions of the lubricating system for starting the operation of said turning gear motor, means for subsequently eflecting.

the connection of said turning gear to said turbine, and means responsive to .a predetermined speed of said turbine for effecting the deepergization of said pump motor and said turning gear motor.

2. In combination with a prime mover having a turning gear including a motor for slowly rotating a rotor of said prime mover during shutdown periods, an auxiliary lubricating system for said prime mover including an oil pump motor, a control switch for said motors effective only during shutdown condition of said prime mover, means controlled by said switch for efiecting the sequential energization of said oil pump motor and said turning gear motor, means automatically operable by said prime mover during starting for deenergizing said motors, andmeans automatically operable by said prime mover upon shutting down for efiecting sequential starting of said pump motor and said turning gear motor.

3. In combination with a turbine, turning gear apparatus including a motor for slowly rotating the turbine rotor during shutdown periods, a motor driven pump for supplying said turbine with lubricant during turning gear operation, means for eifecting the sequential starting of said motor driven pump and the starting of said turning gear motor, means effective only during a predetermined low speed condition of said turbine for efiecting the connection between said turning gear apparatus and said turbine rotor, and means responsive to a predetermined speed of said turbine rotor for eifecting the mechanical disengagement of said turbine rotor and said turning gear apparatus.

4. In combination with a turbine, turning gear apparatus including a motor for slowly rotating the rotor of said turbine during shutdown periods, an auxiliary lubricating system for said turbine including a motor driven pump, means for automatically starting said motor driven pump in response to a predetermined rotor speed during the shutting down operation of said turbine, and means responsive to a predetermined condition of operation of said lubricating system for automatically starting said turning gear apparatus.

5. In combination with a turbine, turning gear apparatus including a motor for slowly rotating the turbine rotor during shutdown periods, means including a motor driven oil pump for lubricating said turbine during turning gear operation, means responsive to the oil pressure, means responsive to oil flow, and means responsive to said pressure and flow responsive means for controlling said turning gear apparatus.

6. In an electrical control system for turbine turning gear apparatus including a motor, a control switch means, a latched-in relay having an operating coil and a trip coil adapted for control by said switch means, means controlled by said relay for starting. said motor, means for automatically efiecting engagement of said turning gear with said turbine, said turning gear being adapted to be automatically disengaged upon said turbine being rotated at a speed greater than normal turning gear speed, and means responsive to the disengagement of said turning gear for precluding tripping of said relay by said control switch means.

7. In an electrical control system for a turbine turning gearapparatus including a motor, control switch means for effecting the starting and stopping of said motor, means for automatically connecting said turning gear to said turbine following the starting of said motor, said turning gear being adapted to be automatically moved to the disengaged position upon said turbine being rotated at a speed greater than normal turning gear speed, means responsive to the automatic disengagement of said turning gear for stopping said turning gear motor, means responsive to a predetermined relatively low turbine speed upon turbine shutdown for restarting said turning gear motor and automatically connecting said turning gear to said turbine.

8. In an electrical control system for a turbine turning gear apparatus having a motor, control switch means, means responsive to the actuation of said control switch for starting said motor, means responsive to the starting of said motor for effecting engagement of said turning gear with the turbine rotor to rotate said turbine rotor at a predetermined speed, said turning gear being adapted to automatically disengage said turbine rotor upon said rotor being rotated at a speed greater than said predetermined speed, and mean responsive to the operative condition of said turning gear whereby said control switch means is rendered effective for stopping said motor only when said turning gear is in the engaged position.

9. In an electrical control system for turbine turning gear apparatus including a motor, control switch means, means normally controlled by said switch means for starting and stopping said motor, means for automatically effecting engagement of said turning gear with said turbine, said turning gear being adapted for automatic disengagement upon said turbine being rotated at a speed greater than the normal turning gear speed, and means responsive to the automatic disengagement of said turning gear for precluding I control of said motor by said switch means.

10. In combination with a turbine, a turning gear apparatus including a motor adapted to be coupled to the turbine rotor for slowly rotating said rotor during turbine shutdown periods, means responsive to a predetermined speed of said turbine by steam for eflecting the uncoupling of said turning gear apparatus from said turbine rotor, and means responsive to a predetermined low turbine speed during the shutting down operation of said turbine for automatically coupling said turbine rotor with said turning gear apparatus.

HERMAN BANY. 

